Control system for a hydraulic work vehicle

Abstract

An apparatus controls an electrohydraulic system of a work vehicle. The work vehicle has a engine, at least one fluid circuit having a variable displacement pump driven by the engine, and a plurality of control valves for controllably passing fluid from the variable displacement pump to a plurality of respective work elements. A device produces a signal indicative of a desired velocity of a respective work element. A device senses a load on a work element and producing a signal representative of the actual load in response to the sensed load. A control device receives the desired velocity signal and load signals, and responsively calculates a desired power level for the electrohydraulic system. Responsively, the control device produces an engine speed command signal indicative of an optimum engine speed in response to the desired power level.

I claim: 
     
       1. An apparatus for controlling an electrohydraulic system of a work vehicle having an engine, at least one fluid circuit having a variable displacement pump driven by the engine, a plurality of control valves for controllably passing fluid from the variable displacement pump to a plurality of respective work elements, each control valve including a stem, comprising: a operator control element adapted to produce a signal indicative of a desired velocity of one of said respective work elements;   a load sensor adapted to detect a load on the one work element and produce a signal representative of the actual load in response to said detected load;   a velocity sensor adapted to determine the velocity of the one work element and produce a signal representative of the actual velocity in response to said determined velocity;   control means for receiving said desired velocity, actual velocity and load signals, responsively calculating a desired and an actual power level for the electrohydraulic system, and responsively producing an engine speed command signal indicative of an optimum engine speed and   an electronic governor adapted to receive said engine speed command signal and responsively control the speed of the engine to the optimum engine speed.   
     
     
       2. An apparatus, as set forth in claim 1, including a means for sensing the speed of said engine and producing a signal representative of the actual speed in response to said sensed speed. 
     
     
       3. An apparatus, as set forth in claim 2, wherein said electronic governor receives said actual speed signal, calculates an error signal proportional to a difference between the magnitude of said engine speed command signal and said actual engine speed signal, and responsively controls the speed of said engine causing the error signal to approach zero. 
     
     
       4. An apparatus, as set forth in claim 1, wherein said control means includes means for calculating a desired pump displacement value in response to said desired velocity signal, and producing a pump displacement command signal indicative of an optimum pump displacement in response to said desired pump displacement value. 
     
     
       5. An apparatus, as set forth in claim 4, wherein said control means includes means for calculating a desired valve stem position value and responsively producing a valve stem command signal. 
     
     
       6. An apparatus, as set forth in claim 5, wherein said electronic governor receives said pump displacement and valve stem command signals, and responsively controls the displacement of said pump to the optimum pump displacement in response to said engine rotating at the optimum speed and the position of the valve stem to the desired stem position in response to said pump producing the optimum pump displacement. 
     
     
       7. An apparatus, as set forth in claim 6, including means for sensing the discharge pressure of said variable displacement pump and producing a signal representative of the actual discharge pressure in response to said sensed pressure. 
     
     
       8. An apparatus, as set forth in claim 7, wherein said variable displacement pump includes a swashplate and said electronic governor includes a means for sensing the angle of the swashplate and producing a signal representative of the actual swashplate angle in response to said sensed swashplate angle. 
     
     
       9. An apparatus, as set forth in claim 8, wherein said electronic governor adjusts the inclination of the swashplate to control the displacement of the pump to the optimum displacement in response to receiving said actual discharge pressure signal and said actual swashplate angle signal. 
     
     
       10. An apparatus, as set forth in claim 6, wherein said variable displacement pump includes a swashplate, and said control means includes a means for receiving said actual velocity signal, calculating an actual pump displacement value and responsively producing an actual pump displacement signal, said electronic governor being adapted to receive said actual pump displacement signal and calculate an error signal proportional to a difference between the magnitude of said pump displacement command signal and actual displacement signal and responsively adjust the inclination of the swashplate to cause the error signal to approach zero. 
     
     
       11. An apparatus, as set forth in claim 6, including a means for sensing the position of a stem relative to a respective control valve and producing a signal representative of the actual position in response to said sensed position. 
     
     
       12. An apparatus, as set forth in claim 11, wherein said electronic governor receives said actual valve stem position signal, calculates an error signal proportional to a difference between the magnitude of said valve stem command signal and said actual valve stem position signal, and responsively controls the position of said valve stem causing the error signal to approach zero.